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Helix Flexibility

Both the model and real DNA helices can be deformed from their
linear shape into curves and bends. Real DNA does this as a result of
normal thermal motion and under the influence of certain proteins which
bind to DNA. The nucleosome which is a DNA packing structure is one
example where DNA is held in a non-linear form. Each nucleosome
consists of a core of histone proteins around which the DNA double helix
is wrapped some 1.6 turns. Other proteins such as DNA transcription
factors also alter the geometry of DNA and thereby modify its ability to
be transcriped into RNA. Above is a model of DNA deformed into a circle.
This requires just over 8 helical turns (50 base pairs). If you build
this model, be sure to attach the same strand to itself when closing
the circle.